Subsea fluid sampling and analysis

ABSTRACT

Subsea apparatus and a method for sampling and analysing fluid from a subsea fluid flowline proximate a subsea well is provided, wherein the apparatus comprises at least one housing located in close proximity to said subsea fluid flowline; at least one fluid sampling device located in the housing in fluid communication with a said subsea fluid flowline for obtaining a sample of fluid from the subsea fluid flowline; at least one fluid processing apparatus located in the housing in fluid communication with said subsea fluid flowline for receiving and processing a portion of the fluid flowing through said fluid flowline or in fluid communication with the fluid sampling device, for processing the sample of fluid obtained from the subsea fluid flowline for analysis, while keeping the sample of fluid at subsea conditions; a fluid analysis device located in the housing, the fluid analysis device being in fluid communication with the fluid processing device and/or with the fluid sampling device, the fluid analysis device being used for analysing said sample of fluid or the processed sample of fluid to generate data relating to a plurality of properties of said sample of fluid and communicating said data to a surface data processor or to at least one other subsea apparatus; and conveying means included in the housing for conveying the housing means from one subsea fluid flowline to another subsea fluid flowline or for conveying the housing to the surface.

BACKGROUND OF THE INVENTION

This invention relates to subsea apparatus for fluid sampling and/oranalysis. In particular, the invention relates to a subsea apparatus forfluid sampling and/or analysis used in the oil and gas industry.

Understanding the properties of fluids in wells in the oil and gasindustry is critical for the assessment of oil or gas reservoirs. Forexample, the fluid properties may be used for the proper management ofoil and gas reservoirs including for instance production management andflow assurance. Fluid sampling and/or analysis may be performed duringvarious phases of the exploration, development and production phases ofa reservoir. Conventional tools are able to take a fluid sample from thewell and bring it to surface where it is processed and analysed. Forexample, often times the phase behavior of the fluid may be studiedusing an analysis known in the industry as PVT analysis which measures,inter alia, the bubble point of the fluid as well as its wax, andasphaltene content. Also, compositional analysis of the fluid sample maybe performed as well as analysis of its H_(2S), CO₂, Hg, and heavy metalcontent. Also, well known are tools and methods for measuring thedensity and viscosity of the fluid its, water content, etc.

More and more of these measurements are arranged to be performeddownhole. This is because, generally, obtaining a correct estimation offluid phase behavior requires that a sample with a pressure andtemperature as close as possible to the conditions present at thewellhead be taken so that wax and asphaltenes do not precipitate out ofthe fluid. Fluid properties at the surface may differ from those presentat the wellhead. Sampling of the fluid at the surface is therefore not asuitable option for the correct estimation of the fluid phase behaviorin subsea oil or gas wells. However, the conditions prevalent in asubsea environment make access to a subsea fluid sample ratherdifficult.

In a subsea oil or gas well installation, fluid flows from differentwell heads are often mixed through a series of manifolds. This poses anadditional complication in the sampling and analysis of subsea wells.Sampling and analysis of the fluid flowing from each individual wellwould be preferred as it would provide a valuable understanding of theproduction capabilities and peculiarities of each well which in turncould be used for proper field management. Also, the properties of thefluid produced by subsea wells may change significantly over a shortperiod of time. Thus, if the analysis of the samples that have beentaken is done at a later time at a surface, the value of the data willbe diminished.

Various apparatus, methods and systems for sampling and analyzing wellfluids have been identified previously. U.S. Pat. No. 6,435,279discloses a method and apparatus for sampling fluids from an underseawellbore utilizing a self-propelled underwater vehicle, and a collectionand storage device. The '279 patent describes a method for sampling afluid produced from a subsea well, the method comprising a remotelyoperated vehicle (ROV) having a collecting device for collecting asample of fluid and a storage facility for the collected sample of fluidwherein said collecting device and storage facility are connected to theROV. The collecting device is used to collect a sample from a subsealocation, storing the sample in the ROV and then transferring it to asurface location.

International patent applications WO 2008/087156, and WO 2006/096659disclose various systems and methods for subsea sampling. The WO2008/087156 patent application describes a subsea sampling and datacollection device that is coupled to a flowline at a flowlineinstallation. The WO 2008/087156 sampling and data collection deviceincludes a sample collection system having a probe insertable into aflowline to collect a fluid sample. The WO 2008/087156 application isassigned to the same assignee as the present invention and it is herebyincorporated by reference for all purposes allowable under the law tothe extent that its disclosure does not contradict with the presentinvention.

An article entitled “Improved production sampling using the Framomultiphase flow meter” by Framo Engineering AS in October 1999 discussesa multiphase flow meter used in fluid sampling, including subsea withthe aid of remotely operated vehicles (ROV).

From the description above it is evident that for effective productionand flow assurance management in subsea oil and gas reservoirs, there isa real need to obtain a good understanding of produced fluid on a wellby well basis and to measure the variation of fluid properties from eachof these wells with time. The present invention provides an improvedapparatus and associated method that facilitate the sampling and thecharacterization of the fluids at a subsea environment, and as close aspossible to each well head. The present invention and method also enableanalysis of sampled fluid to occur on a real time basis and thus obtainaccurate real time analysis data for well performance and management.

BRIEF SUMMARY OF THE INVENTION

A first aspect of this invention provides subsea apparatus for samplingand analysing fluid from a subsea fluid flowline proximate a subseawell, comprising:

-   -   at least one housing located in close proximity to said subsea        fluid flowline;    -   at least one fluid sampling device located in the housing in        fluid communication with a said subsea fluid flowline for        obtaining a sample of fluid from the subsea fluid flowline;    -   at least one fluid processing apparatus located in the housing        in fluid communication with said subsea fluid flowline for        receiving and processing a portion of the fluid flowing through        said fluid flowline or in fluid communication with the fluid        sampling device, for processing the sample of fluid obtained        from the subsea fluid flowline for analysis, while keeping the        sample of fluid at subsea conditions;    -   a fluid analysis device located in the housing, the fluid        analysis device being in fluid communication with the fluid        processing device and/or with the fluid sampling device, the        fluid analysis device being used for analysing said sample of        fluid or the processed sample of fluid to generate data relating        to a plurality of properties of said sample of fluid and        communicating said data to a surface data processor or to at        least one other subsea apparatus; and    -   conveying means included in the housing for conveying the        housing means from one subsea fluid flowline to another subsea        fluid flowline or for conveying the housing to the surface.

The fluid analysis data can be real time data, and this real time datais communicated to at least one electronic device which incorporates atleast one software model used to provide information regarding theproduction of said subsea well. The software model may also used toprovide predictions regarding the production of the well.

In one form of the invention the fluid analysis data is used to controlat least one piece of subsea equipment. The fluid processing apparatusseparates the sample of fluid into at least a liquid and a gaseousphase, or mixes the sample of fluid with at least one other differentfluid, or enriches the sample of fluid.

In one form of the invention the fluid sampling device is incommunication with the well fluid. The fluid sampling device may also bein communication with a fluid processing apparatus, the fluid processingapparatus being in communication with the well fluid.

Further according to the invention, at least one data processing devicemay be locatable in the housing and may be in communication with thefluid analysing device. The data processing device processes datareceived from the fluid analysis device and communicates the data.

The conveying means may be an attachment for a detachable subsea vehiclesuch as, for example, a remotely operated vehicle (ROV) or an autonomousunderwater vehicle (AUV).

The subsea apparatus may further comprise a plurality of housings whichare connectable to each other in a modular fashion. The fluid analysisdevice of each housing may be in fluid communication with the fluidanalysis device of another connected housing. In the same way, the fluidsampling device of each housing may be in fluid communication with thefluid sampling device of another fluid sampling device of a connectedhousing, and the data processing device of each housing may be in fluidcommunication with the data processing device of a connected housing.

A second aspect of this invention provides a method of sampling andanalysing fluid from a subsea well, the method comprising:

-   -   locating at least one housing in close proximity to a subsea        flowline proximate said subsea well, said housing comprising at        least one fluid analysis device, at least one fluid processing        apparatus and at least one fluid sampling device, the fluid        sampling device being in fluid communication with said subsea        flowline, the fluid processing apparatus being in fluid        communication with said subsea flowline and/or with the fluid        sampling device, the fluid analysis device being in fluid        communication with the fluid processing device and/or with the        fluid sampling device;    -   obtaining a sample of fluid from the subsea flowline, and        storing it in the fluid sampling device;    -   transferring the sample of fluid to the processing device, and        processing the sample of fluid with the processing device for        analysis by the fluid analysis device, while keeping the sample        of fluid at subsea conditions;    -   transferring the sample of fluid from the processing device to        the fluid analysis device;    -   analysing the properties of the fluid with the fluid analysis        device to obtain fluid analysis data subsea;    -   communicating the fluid analysis data to at least one other        subsea apparatus or to a surface data processor; and    -   conveying the housing from said subsea fluid flowline to another        subsea fluid flowline or to the surface.

In one form of the invention the fluid sampling device is in fluidcommunication with a fluid processing apparatus, the fluid processingapparatus being in fluid communication with the well fluid flowing inthe subsea flowline and the sample of fluid is obtained from the wellfluid in the subsea flowline via the fluid processing apparatus. Thefluid sampling device may also be in communication with a fluidprocessing apparatus that is in communication with the well fluid.

Further according to the invention, at least one data processing devicemay be locatable in the housing and may be in fluid communication withthe fluid analysis device, and which further comprises processing fluidanalysis data received from the fluid analysis device by means of thedata processing device and communicating the processed data to anotherapparatus or to the surface. The method may further include processingfluid data received from the fluid analysis device and communicating thedata.

The method may also comprise deploying one or more housings of theapparatus by means of a detachable subsea vehicle such as, for example,a remotely operated vehicle (ROV) or an autonomous underwater vehicle(AUV), the housings being connectable to each other.

In a further form of the invention there may be a plurality of housings,and the method may further comprise connecting the plurality of housingsto each other in a modular fashion, and wherein each fluid analysisdevice of each housing is in fluid communication with each other, andeach fluid sampling device of each housing is in fluid communicationwith each other.

Further aspects of the invention will be apparent from the followingdescription.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING

FIG. 1 shows a schematic side view of a subsea apparatus for samplingand/or analysing fluid from a well according to one embodiment of theinvention;

FIGS. 2 shows a schematic side view of a housing of the subsea apparatusfor sampling and analysing fluid from a well as shown in FIG. 1,attached to a remotely operated vehicle (ROV);

FIG. 3 shows a schematic side view of the subsea apparatus for samplingand/or analysing fluid attached to a fluid processing device indicatingthe flow direction through the components of the fluid processingdevice;

FIG. 4 shows a diagrammatic view of a hydraulic sampling device of thesubsea apparatus for sampling and/or analysing fluid from a wellaccording to one embodiment of the invention;

FIG. 5 a shows a diagrammatic view of a passive sampling device of thesubsea apparatus for sampling and/or analysing fluid from a wellaccording to another embodiment of the invention;

FIG. 5 b shows a diagrammatic view of a passive sampling device of thesubsea apparatus for sampling and/or analysing fluid from a well whichuses venturi according to another embodiment of the invention;

FIG. 6 shows a diagrammatic view of an active sampling device of thesubsea apparatus for sampling and/or analysing fluid flow which uses apump according to a further embodiment of the invention;

FIGS. 7 a, 7 b and 7 c show a series of diagrammatic views of anadjustable inlet of a sampling device according to an embodiment of theinvention;

FIG. 8 shows a schematic layout of a fluid analyser of the subseaapparatus for analysing fluid from a well;

FIG. 9 shows a schematic side view of a section of an in-line fluidanalyser of the subsea apparatus for sampling and analysing fluid from awell according to one embodiment of the invention;

FIG. 10 shows a schematic side view of a section of an in-line fluidanalyser of the subsea apparatus for sampling and analysing fluid from awell which includes a phase behaviour fluid analyser according toanother embodiment of the invention;

FIGS. 11, 11 a, 11 b and 11 c show schematic side view of a samplingbottle for low shock sampling with a piston inside the bottle of thesubsea apparatus according to one embodiment of the invention;

FIGS. 12, 12 a, 12 b and 12 c show schematic side view of a samplingbottle for low shock sampling without a piston inside the bottle of thesubsea apparatus according to one embodiment of the invention;

FIG. 13 shows schematic view of a self retrievable sampling bottleapparatus of the subsea apparatus according to one embodiment of theinvention; and

FIG. 14 shows a schematic overview of a controller configuration usedfor the control of a number of subsea apparatuses according to oneembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

This subsea apparatus for analysing and/or sampling fluid from a wellaccording to the invention is applicable to subsea installations orfacilities in the oil and gas industry. In the drawings FIG. 1illustrates the basic layout of a subsea apparatus 10 for samplingand/or analysing fluid from a well according to the invention. Subseaapparatus 10 is located in close proximity to the wellhead of a well andincludes a subsea fluid processing device 12 for processing fluidsamples obtained from the well. The subsea processing device 12 can be aphase separator, a phase accumulator, a boosting pump, a water treatmentunit, chemical injector or an injection pump, depending on theapplication required.

The subsea processing device 12 includes a fluid sampling device 14. Thefluid sampling device 14 consists of a network of pipes connected todifferent sampling points in the processing device 12. The fluidsampling device 14 can also include a distributor that can redirect thesampled fluid to different outlet.

Subsea apparatus 10 further includes a remote operating device (ROV)docking station 16 which allows the docking and attachment of a remoteoperating device (ROV) 18 to the subsea processing device 12.

As shown in FIG. 1, there is a fluid interface 20 in communication withthe sampling device 14 which is located below the ROV docking station16. The fluid interface 20 allows a hydraulic connection between the ROV18 and the processing device 12, and thus fluid at well pressure cantravel between them. This hydraulic connection can be initiated when theROV 18 is docked at the docking station and it can be disconnected whenthe ROV 18 is removed.

A frame or skid 22 could also be docked to the docking station with thehelp of an ROV 18. As illustrated in FIG. 2, the skid 22 is attached tothe ROV 18 with several instrumentation modules connected thereto. Thiswill be further described below. Skid 22 can be docked to the dockingstation 16 as the ROV 18 approaches the installation. The skid 22 canthen be detached from the ROV 18 through a specific skid/ROV interface24 and it can then be left permanently on the installation of apparatus10. The skid/ROV interface 24 may be a fluid interface and skid 22 is incommunication with the fluid interface 20. By using a hydraulicconnection between skid 22 and fluid interface 20, the well fluid can bedirected to the instrumentation module 26 which is located on the skid22.

Skid 22 is designed so that other skids 22 of a similar type can beconnected to it. The design is modular so that the skids 22 can beconfigured and assembled in different orders, and then used fordifferent purposes.

Skid 22 can also be deployed using an autonomous under water vehicleAUV. In this case, the skid interface 24 may include instrumentation forthe positioning of the AUV during docking.

An instrumentation module 26 is located inside skid 22 and is connectedto a controller/communication module 28. Instrumentation module 26contains the fluid analyzer and it is used to perform fluid analysisand/or fluid sampling. It is connected to the fluid interface 20 and itcan receive the fluid collected by the fluid sampling device 14. Thetype of analysis and the sampling sequence is managed by thecontroller/communication module 28. The controller/communication module28 performs control either through a pre-defined sequence stored in thecontroller, from the surface with the use of a communication link, or ina completely automated mode with the use of the fluid analysis dataobtained by the fluid analyzer in instrumentation module 26. It is usedto enable decisions to be made on how to process the sample of fluid.

There are various different possible schemes for the sampling which havebeen described previously in the art and these can easily be implementedin conjunction with this invention.

The fluid analyzer in instrumentation module 26 consists in a network ofpipe connected to pumps, fluid properties sensors, sample chambers,fluid conditioners and injectors. This system is managed through thecontroller/communication module 28.

The fluid analysis data obtained by apparatus 10 is used to controlvarious types of subsea or surface equipment. This fluid analysis datais based on real time sample measurements obtained from the fluid samplethat is obtained and also possibly analyzed at wellhead conditions. Thisreal time fluid data may be communicated to an electronic device whichincorporates at least one software model and this model may be used toprovide information regarding the production of the well and to providepredictions regarding the production of the well. Thus informationregarding reservoir assurance, or flow assurance management may beobtained through the processing of this fluid data.

Details will now be provided of further embodiments of the invention.

FIG. 3 illustrates an embodiment of the subsea apparatus for samplingand/or analysing fluid from a well according to the invention, whichfurther includes a phase separator 30.

The phase separator 30 which may be used is one of the typical examplesof phase separators known in the art. Such a typical phase separatorconsists of a pressure vessel 32 with an internal pipe drilled withradial holes. The pressure vessel 32 includes a fluid inlet 34 and fluidoutlet 36. The direction of fluid flow is shown by arrows A in FIG. 3.The phase generator 30 was initially designed in the art as a device forfluid mixing purposes but it can also be used as a fluid separator. Inthe pressure vessel area, the fluid segregates depending on its density,with gas separating out on top and the liquid (oil and water) separatingout at the bottom. As the fluid is forced through the central pipe (withholes), the phases are remixed, leading to a mixed fluid flow leaving atthe outlet.

Phase generator 30 allows liquid can be sampled at the bottom of thevessel while gas can be sampled at the top.

FIG. 3 further shows a retrievable ROV 18 with a skip 22 including afluid sampling or analysis module 26 to be used for fluid sampling, aswell as a skip 22 including a fluid sampling or analysis module 26 to beused for fluid analysis, and then a multi-phase flow meter 38.

The hydraulic sampling device of apparatus 10 is illustrated in FIGS. 5and 6. Fluid sampling can be done either through a passive or an activesampler. In the implementation of the invention shown in FIGS. 5 and 6,the fluid sampling or analysis module 26 has internal piping connectingthe liquid sampling pipe 44 to the gas sampling pipe 46. It furtherincludes an inlet pipe 40 to sample the fluid from the separator to thefluid analyzer in module 26 and an outlet pipe 42 to re-inject the fluidto the separator or main fluid flow line after it has been analyzed. Thedirection of fluid flow is shown in FIGS. 5 a, 5 b and 6 by arrows B.

Passive sampling devices 26 do not require any pump to sample the fluidas these devices are based on passive mechanisms. Two different possibleimplementations of passive sampling devices are shown in FIGS. 5 a and 5b. In FIG. 5 b, the fluid movement inside the sampling tubes isgenerated using a venturi device 48. The outlet pipe 42 is connected toventuri device 48 which is located further down the fluid flow line. Theventuri device 48 generates a pressure difference that drives the fluidthrough the piping system and the fluid sampling or analysis module 26or from the inlet to the outlet.

In FIG. 5 a, the fluid in the extraction line is dragged by the mainflow in a perforated pipe 50.

FIG. 6 describes an active sampler using a pump 52 to generate the fluidflow from the inlet to the outlet.

In practice several different types of fluid sampling devices can beused. For example, in FIGS. 5 and 6, with the use of the proposedseparator, it is possible to change the sampled liquid phase byadjusting the position of the inlet inside the phase separation chamber.The liquid phase of the fluid will accumulate at the bottom while thegas phase will accumulate at the top of the vessel.

One possibility is to have two or more inlet pipes 40.1 and 40.2 withdifferent heights as is illustrated in FIG. 7 a. If required, the flowfrom these sampling pipes could be directed to a manifold before beingrouted to the fluid sampling or analysis module 26.

Another possibility which is described in FIG. 7 b is to have a samplingpipe with an adjustable height that is adjustable with the use ofmechanical actuators 56. The height H may then be adjusted according towhat is required. With time, the ratio between the different phases offluid produced by the well changes. With such an adjustable samplinginlet, it is thus possible to adapt the sampling device to the changesin production conditions.

FIG. 7 c describes an adjustable fluid sampling or analyzing module 26which uses a series of controllable valves 57 and 58 connected theretoto change the sampling point position. The valves 57 and 58 can beselectively closed. In the normal operation, all valves 58 are closedexcept for the valve 57 which is at the level of the sampling point. Thefluid flow is illustrated in FIG. 7 by arrows E.

In one embodiment of the invention there is a universal skid 22 used forfluid sampling and analysis. This skid 22 includes the fluid interface20, power/communication module 28, skid or ROV interface 24, a localcontroller module and a fluid sampling or analysis module 26. The localcontroller module controls the working of the sampling or fluid analysismodule 26.

One feature of apparatus 10 is its modularity. Apparatus 10 may beprovided in different kinds of modules. Fluid, communication and skid orROV interfaces are designed to be fully interoperable so that differentkinds of modules of apparatus 10 can be interconnected and configured inmany different types of configurations.

Another feature of apparatus 10 is that modules of apparatus 10including skids 22 may be installed either on a temporary basis or on asemi-permanent basis.

Before any fluid sampling or fluid analysis operation starts, the skids22 are fully engaged in an ROV 18 and connected to the various fluidinterfaces. An individual module of apparatus 10 comprising a skid 22and its attached equipment can be retrieved as required by an ROV 18.

The fluid sampling or analyzing device 26 which is mounted in a skid 22in apparatus 10 is shown in more detail in FIG. 8. The device 26 isenclosed in a tool housing 59 and it includes fluid flow lines 60connected together and guiding the fluid from an inlet to an outlet. Thedevice 26 further includes pumps 62 which can move the fluid therethrough. Fluid conditioners 64 which are used to process the fluid andchange properties such as the ratio between the different fluid phases,or the fluid pressure, volume or temperature are also included in device26. Fluid processing devices 12 may further include a separator, amixer, and a PVT (pressure, volume and temperature) device.

In device 26 injectors 66 can be used to inject fluids which aredifferent from the fluid which is flowing in a particular flow line 60.The injected fluid can be used to generate an inhibitory chemicalreaction with the sampled fluid or it can change the phase behavior ofthe fluid. Sample bottles or chambers 68 in device 26 are used to takeand store samples of the fluid inside a flow line 60. Fluid propertysensors 70 are also shown located on flow lines 60 in device 26.

In the drawings, FIG. 9 illustrates an embodiment of the fluid samplingor analysis device 26 of apparatus 10 to be used for fluid analysis withone possible configuration of sensors 70. In this embodiment, device 26is in-line with the sampling piping. Various types of sensors 70 areshown in the in-line configuration in a fluid flow line 60. Thesesensors may be, for example, a lamp 72 and spectrophotometer 74arrangement, a fluorescence detector 76, a resistivity sensor 78, anX-ray or gamma ray density sensor 80, a pressure and temperature gauge82, a density or viscosity sensor 84, a vibrating wire 86, an in-lineCO2 sensor 88, or an in-line H2S sensor 90. In FIG. 9 the fluid sampleis shown to flow in either direction through the flow line 60.

The fluorescence detector 76 can be used to, for example, detect tracesof oil in water. This information can be useful for the assessment ofsubsea processing, for example, when water is separated from oil beforebeing re-injected into the formation.

The fluid resistivity sensor 78 can be used to detect water resistivity,which can be very useful information which can in turn be used to detectinjection water breakthrough. Injection water used for reservoirstimulation will usually have a resistivity different from that offormation water. Water resistivity changes, therefore, can be correlatedwith injection water breakthrough.

The fluid sampling or analysis device 26 can also include fluidconditioners. One possible fluid conditioner is a phase separator. Thiscan be used for water or oil sampling. The main phase separator willgive a liquid or gas separation. The phase separator within the fluidsampling or analysis device 26 can therefore be used to separate the oilfrom the water if necessary.

Another sensor which may form part of device 26 is a unit to “flash” thesample. Sample flashing consists of dropping the pressure of samplebefore injecting it with a specific sensor. This method is well known inthe analysis of HP (high pressure) live oil samples by using gaschromatography.

The embodiment of device 26 which is illustrated in FIG. 9 is suitablefor different types of application. These could include, for example,NMR characterization for composition analysis or viscosity measurement,gas chromatography, mass spectroscopy, inductive coupled plasma chemical(ICP) analysis, electro-chemical sensors, or pH or ion concentrationmeasurement in water phase using colorimetric methods.

In the drawings, FIG. 10 illustrates a further embodiment of apparatus10 of the invention which includes a fluid sampling or analysis device26 to be used for fluid analysis that has a further possibleconfiguration of sensors 70. Device 26 in this embodiment can be usedfor several types of measurement. Device 26 includes two seal valves 92and 94 that can be opened and closed in order to trap a fluid sample inbetween them. The volume of fluid in the piping system between the twoseal valves 92 and 94 forms a fluid circulation loop. The fluid in thecirculation loop can be circulated with the circulation pump 96 and pumpunit 103. Seal valve 98 is used to force the fluid flow through thecirculation loop before valves 92 and 94 are closed.

A piston unit that is used to increase the volume trapped between theseal valves and consequently to reduce sample pressure. There is apressure sensor connected to the circulation loop to monitor pressurechanges as the piston is retracted. The piston is preferably retractedwhen the circulation pump 96 is operating. The agitation created by thefluid moving helps to prevent a problem posed by fluid supersaturation.It is well-known in the art that estimation of bubble point requiressome agitation as the pressure is changed. The circulation loop caninclude an ultrasonic transducer that will also generate agitation andthis helps to prevent supersaturation.

A scattering detector 100 sensor is used in device 26 in order to detectbubbles or solid particles forming in a fluid flow line 60. Thescattering detector 100 used is known in the art and is used to measurethe attenuation of light as it passes through a cell. Formation of solidparticles and gas bubbles will lead to an increase in the attenuation oflight. This sensor is used to detect the fluid bubble point whichindicates at which pressure gas starts to form in the flow line. Suchsensors can be used to detect the gas condensate dew point, the fluidbubble point, gas bubble formation or the presence of solid particles.

A density and viscosity sensor 84 may also be included in device 26. Itis used to measure the evolution of the parameters of density andviscosity against pressure.

An optical spectrometer (the lamp 72 and spectrometer 74 arrangement)may also be included in device 26 to measure fluid optical absorption atvarious wavelengths. The optical spectrometer, for example, can be usedto estimate fluid composition by NIR spectroscopy. It is of particularinterest for hydrocarbon analysis as the hydrocarbons havecharacteristic absorption peaks around [1600; 1800] nm. Spectralanalysis in the visible range can also be used for monitoring asphaltenecontent of the fluid.

Device 26 may also include a camera 102 which is used to monitor thecondition of the fluid in the flow lines for the presence of bubbles orsolid particles. In addition, device 26 may also enclose a US transducersensor 104.

Device 26 may be enclosed in a temperature control unit 106. Thetemperature control unit 106 may enable the temperature of the fluid tobe changed. In this way by combining pressure and temperature changes,device 26 can provide a comprehensive phase diagram for the fluidtrapped in the fluid flow lines 60 of the device.

Device 26 may be used in various downhole conditions and can be used invarious applications such as, for example, the study of fluid phasediagrams (bubble point detection, wax or asphaltene onset, hydratelocus, etc), the study of fluid density and viscosity versus pressure,and the study of fluid composition.

Another important feature of the invention is the ability to samplefluid. FIG. 11 gives a possible configuration for a sampling bottle 108.The sampling bottles 108 of apparatus 10 are configured for low shocksampling. Low shock sampling comprises filling a bottle 108 with thesample with a controlled flow rate. The goal is to avoid fast pressurechanges of the sample which could lead to phase transition before thebottle 108 is filled.

The sampling bottle 108 can be implemented as follows:

A cylindrical bottle 108 with a piston 110 defining two chamber spacesas it moves along the bottle's main axis. The sample chamber 112 islocated on one side of piston 110 is and the water cushion chamber 114is located on the other side of piston 110.

Bottle 108 is connected to the fluid sampling line as shown in FIG. 11.In the initial position before the bottle 108 is opened, shown in FIG.11 a, the volume of sample chamber 112 is minimal while the cushionwater chamber 114 side is full. For sampling, the solenoid valve 116 andthe choke valve 118 are opened. The rate of sampling can be controlledby the choke 120. The choke 120 controls the fluid flow and thereforethe fluid flow rate in the sample chamber 112. The sampling is completedonce the piston 110 reaches its final position on the other side of thebottle 108. Both the solenoid valve 116 and the choke 120 can be closed.Due to the controlled flow rate, the fluid is sampled with minimumpressure changes.

It will be noted that low shock sampling can also be done without thepiston 110 being in the bottle as shown in FIG. 12 c. In this case, thesampling bottle 108 must be flashed long enough to remove any of theinitial filling water. FIG. 11 b illustrates bottle 108 during sampling.

Low shock sampling is a well known technique for downhole fluidsampling. Other possible variations of fluid sampling have also beendescribed in the prior art.

The fluid sampling can be controlled either from surface or it can becontrolled through a predetermined sequence of actions to be taken on aperiodic base.

The combination of the fact that the fluid sampling or analysis device26 can be installed on a semi-permanent basis, the configuration of thesampling skid 22 and the possibility that sample can be obtained on aperiodic basis, means that it is possible to sample the fluid withoutmobilizing an ROV 18 with its support vessel. Device 26 can thereforeperform time-lapsed sampling during the time it is installed on a subseaapparatus 10. With the proposed configuration, the sampling can beperformed though period of time from a few months to a few years. Samplebottles 108 can be retrieved at the surface by using an ROV 18 to pickup the skid 22 on which the sample bottles 108 are located.

A sampling bottle 108 may also include a temperature control unit 122.Temperature control allows the sample temperature to be kept the same aswhen it was in the fluid flow of the well. It would avoid phasetransition due to temperature changes. In practice, the sample will tendto cool when it is sent to the bottle 108. The temperature controlsystem can consist of a simple electrical heating system wrapped aroundthe bottle.

Another important feature of the invention is the ability of samplingbottles 108 to be retrieved to the surface before the skid 22 ischanged. The bottle 108 may include means for energy storage, apositioning system and a propulsion mechanism. An embodiment of theapparatus 10 according to the invention which illustrates such aconfiguration of a sample bottle 108 is shown in FIG. 13. The bottle 108in this embodiment is filled with compressed gas. An inflatablestructure such as a balloon 124 is connected to the bottle 108 that isfilled with compressed gas. The balloon 124 is connected to thecompressed gas through a solenoid valve 116.

The bottle 108 end fittings use male/female hot stabs 107 that can bereleased through a command sent from the skid controller. The bottle 108is fixed to the skid chassis through a mechanical interface that canalso be released by a command sent by the skid controller. The bottle108 also includes a localization system that can communicate with thesurface. When the bottle 108 needs to be released a command is sent fromthe surface and this triggers the inflation of the balloon 124, as wellas the release of the end fitting and mechanical interface. In additionthis also activates a localization beacon 126. The bottle 108 is thenbuoyed to the surface. Once back at surface, the bottle 108 can belocated and retrieved by a surface support vessel 128.

In FIG. 4 of the drawings the fluid sampling section and the skids areshown to be in a modular configuration. The fluid sampling device 26 isconfigured according to the configuration described in FIG. 5 a. Thedevice 26 includes two sampling lines located at different heights as isdescribed in FIG. 7 a. The longer sampling line will sample liquid whilethe other shorter one will sample gas. An extraction pipe 130 is commonto the gas 44 and liquid 46 sampling pipes. They form two primary loopsthrough which production fluid circulates.

The mechanical and hydraulic fluid interfaces are based on standardizedstab plates 134 including electrical and hydraulic connections, as wellas hydraulic valves 136 and 138. The valves 138 are closed when a skid22 is engaged on top of it. In all other circumstances the valves 136and 138 are open. The mechanical interfaces of the stab plates 134 andvalves 136 and 138 are the same on top of the phase separator as theyare on the skids 22. In this way the skids 22 can be stacked in anyconfiguration on top of the separator 30.

The valves 136 and 138 are configured to connect the fluid samplinglines 46 with the extraction line 130. As the skids 22 are connected oneon top of another, the valves 138 from the lower skids are closed whilethe upper valves 136 are opened. The valves 138 of the lower skid 22 areclosed when the upper skid connects to it. This takes place afterhydraulic connection is completed. The configuration of the valves 136and 138 allows the liquid to circulate from the separator 30 to theupper skid 22.

Fluid sampling and analysis devices 26 are located between the samplingpipes 44 and the extraction pipes 130. There may be a pump 132associated with these devices 26 in order to circulate the fluid fromthe sampling line 44 to the extraction line 130. This configuration asshown in FIG. 4 allows for a fully modular configuration.

Another important feature of the invention is the use of subsea fluidanalysis measurement by apparatus 10 to be used to control subseaequipment. The information from the apparatus 10 can be used, forexample to control subsea equipment in a fully automated mode, or tocontrol subsea equipment from the surface using the information obtainedfrom apparatus 10. Different controllers/communication modules 28 areconnected in a network configuration with, for example, an Ethernetarchitecture, which allows communication and control between thedifferent skids 22. The information can either be sent to the surface orprocessed at seabed level for the direct management of the control ofother subsea modules.

In a fully automated mode, the information obtained from the sensors isdirectly processed at the seabed and a decision is made at subseaapparatus 10. The information can be used to optimize choke opening forexample. Another possible example is the optimization of chemical orwater injection and the optimization of phase separator operatingconditions. The information can also be sent to the surface for humanbased interpretation and decision making.

FIG. 14 shows one embodiment of the subsea apparatus 10 and methodaccording to the invention in which a template of fluid platforms arelocated on the seabed. FIG. 14 illustrates the flow of fluids fromdifferent wellheads which are mixed through sets of manifolds beforebeing sent to the surface. Fluid platforms are shown placed between awellhead and a manifold. This configuration enables the production fluidflow of each individual well to be characterized.

Another important feature of the subsea apparatus 10 and methodaccording to the invention is the ability to combine the measurementsobtained from the fluid sensors of devices 26 in apparatus 10 with themeasurements obtained from other sensors on the seabed.

One possibility is to combine fluid analysis results with multiphaseflow meter measurement for flow assurance prediction. The measurementresults can be fed to simulation software such as OLGA® to predictpossible flow assurance problems along the subsea installation. Forexample, in a case where OLGA® is handling 1D dynamic simulation offluid phase behavior along the subsea piping installation. It allowssimulation from the wellhead to the surface. Critical inputs for thistype of software are phase diagrams as well as the respective flow ofeach phase (water, oil and gas) of the fluid. A phase diagram of eachphase can be obtained from a PVT sensor as illustrated in FIG. 10.

Another possibility is the use of composition measurement. A gaschromatograph could be installed on the fluid sampling or analysisdevice 26 to be used for analysis so as to provide the detailedcomposition. Combined with equation of state this could provide a phasediagram for each phase.

The apparatus 10 and method according to this invention in combinationwith multiphase flow meter data may be used to obtain real-time flowassurance prediction by feeding fluid properties directly into thesoftware models that are used for this purpose. This would allow thecontrol of subsea equipment to optimize production condition.

Flow assurance problems are likely to happen during installationshut-down, therefore, providing updated information on fluid behaviorjust before the shut-down would be able to help provide bettermanagement of the installation.

Another possible application of the apparatus and method according tothe invention is its use for the optimization of chemical injection.Many chemicals are injected at different points in a subsea installationto manage a flow assurance problem. By sampling the fluid at theinjector output after the inhibitor is mixed with the production fluid,it is possible to assess the efficiency of the chemical treatment andoptimize the quantity of chemical to be injected. For example, themeasurements of a phase behavior analyzer can be used to assess theefficiency of the treatment. By comparing the phase behavior in realtime, with the operation safety envelop, it is possible to optimize thevolume or the type of chemical injected.

The measurement from the fluid sampling or analysis device 26 can alsobe used for a more accurate estimation of the flow rate from each of thedifferent phases from a multiphase flowmeter. An important inputparameter of a multiphase flow meter used in the oil and gas industry isthe density of each phase. The fluid analysis device of FIG. 9 couldprovide an estimation of the density of each phase that could befeedback in real-time to the multiphase flow meter for a more accurateestimation of individual flow rate.

In the subsea configuration of equipment illustrated in FIG. 14, thefluid flow from the different wellheads is mixed through the manifoldsbefore being brought back to the surface. The problem of identifying thecontribution of each well is known in the art as allocation. The fluidsbefore mixing can come from different formations and from different payzones. In addition, operators may sometimes share export lines. In termsof revenue sharing, allocation is extremely important. For allocation,fluid properties as well as flow rate must be considered. Further, interms of fluid properties, from an allocation standpoint, the importantparameters are H2S content, CO2 content as well as hydrocarbon phasecomposition. Therefore fluid analysis data obtained from the apparatus10 could be used for real time correction of allocation calculation.

1. Subsea apparatus for sampling and analysing fluid from a subsea fluidflowline proximate a subsea well, comprising: at least one housinglocated in close proximity to said subsea fluid flowline; at least onefluid sampling device located in the housing in fluid communication witha said subsea fluid flowline for obtaining a sample of fluid from thesubsea fluid flowline; at least one fluid processing apparatus locatedin the housing in fluid communication with said subsea fluid flowlinefor receiving and processing a portion of the fluid flowing through saidfluid flowline or in fluid communication with the fluid sampling device,for processing the sample of fluid obtained from the subsea fluidflowline for analysis, while keeping the sample of fluid at subseaconditions; a fluid analysis device located in the housing, the fluidanalysis device being in fluid communication with the fluid processingdevice and/or with the fluid sampling device, the fluid analysis devicebeing used for analysing said sample of fluid or the processed sample offluid to generate data relating to a plurality of properties of saidsample of fluid and communicating said data to a surface data processoror to at least one other subsea apparatus; and conveying means includedin the housing for conveying the housing means from one subsea fluidflowline to another subsea fluid flowline or for conveying the housingto the surface.
 2. Subsea apparatus as in claim 1, further comprising atleast one electronic device which incorporates at least one softwaremodel used to provide information regarding the production of saidsubsea well.
 3. Subsea apparatus as in claim 1, wherein the fluidanalysis data is used to control at least one subsea piece of equipment.4. Subsea apparatus as in claim I, wherein the fluid processingapparatus separates the sample of fluid into at least a liquid and agaseous phase, or mixes the sample of fluid with at least one otherdifferent fluid, or enriches the sample of fluid.
 5. Subsea apparatus asin claim 1, wherein at least one data processing device is located inthe housing and is in communication with the fluid analysis device. 6.Subsea apparatus as in claim 1, wherein the conveying means is anattachment for a detachable subsea vehicle.
 7. Subsea apparatus as inclaim 6, wherein the conveying means is an attachment for a remotelyoperated vehicle (ROV) and/or an autonomous underwater vehicle (AUV). 8.Subsea apparatus as in claim 1, which comprises a plurality of fluidanalysis devices which are connected to each other.
 9. Subsea apparatusas in claim 1, which comprises a plurality of housings connected to eachother in a modular fashion located in close proximity to said subseafluid flowline, and wherein each fluid analysis device of each housingis in fluid communication with each other, and each fluid samplingdevice of each housing is in fluid communication with each other.
 10. Amethod of sampling and analysing fluid from a subsea well, the methodcomprising: locating at least one housing in close proximity to a subseaflowline proximate said subsea well, said housing comprising at leastone fluid analysis device, at least one fluid processing apparatus andat least one fluid sampling device, the fluid sampling device being influid communication with said subsea flowline, the fluid processingapparatus being in fluid communication with said subsea flowline and/orwith the fluid sampling device, the fluid analysis device being in fluidcommunication with the fluid processing device and/or with the fluidsampling device; obtaining a sample of fluid from the subsea flowline,and storing it in the fluid sampling device; transferring the sample offluid to the processing device, and processing the sample of fluid withthe processing device for analysis by the fluid analysis device, whilekeeping the sample of fluid at subsea conditions; transferring thesample of fluid from the processing device to the fluid analysis device;analysing the properties of the fluid with the fluid analysis device toobtain fluid analysis data subsea; communicating the fluid analysis datato at least one other subsea apparatus or to a surface data processor;and conveying the housing from said subsea fluid flowline to anothersubsea fluid flowline or to the surface.
 11. The method as in claim 10,wherein the fluid sampling device is in fluid communication with a fluidprocessing apparatus, the fluid processing apparatus being in fluidcommunication with the well fluid flowing in the subsea flowline and thesample of fluid is obtained from the well fluid in the subsea flowlinevia the fluid processing apparatus.
 12. The method as in claim 10,wherein at least one data processing device is locatable in the housingand is in fluid communication with the fluid analysis device, and whichfurther comprises processing fluid analysis data received from the fluidanalysis device by means of the data processing device and communicatingthe processed data to another apparatus or to the surface.
 13. Themethod as in claim 10, wherein the conveying means is an attachment fora detachable subsea vehicle.
 14. The method as in claim 10, whereinthere are a plurality of housings, and which further comprisesconnecting the plurality of housings to each other in a modular fashion,and wherein each fluid analysis device of each housing is in fluidcommunication with each other, and each fluid sampling device of eachhousing is in fluid communication with each other.